The basic objective of this research is to identify physiological regulators of synaptosomal amino acid transport. We have found that serum albumin stimulates the uptake of proline by synaptosomal fractions and the site responsible for the stimulatory effect has been identified as the same site that is responsible for fatty acid binding also. These observations raise the interesting possibility that free fatty acids may regulate synaptosomal transport of amino acids (and perhaps of several putative neurotransmitters as well). This possibility will be investigated in detail in the proposed investigations.